First, you can better ask questions like these in the Tech forum. I assume you posted here because of the "How-to" in the name, but this forum is meant for actual guides, not questions. The Tech forum is frequented better than this one, so you'll have a bigger chance of getting your questions answered.

Iiuc, you want to pass a parameter to a web screen, but you don't want the user to be able to see the content? I can say two things about that:
1) Since you need to decrypt the parameter in the Preparation of the receiving screen, you need a reversable encryption. This is always bad. If you have a smart user, they may be able to figure out the encryption used, and pass wrong parameters anyway. Don't do that!
2) As a solution, you may use a database entity that is associated with a unique key, preferably a GUID. You can then pass the GUID to the web screen, and in the screen's Preperation, you can read the database using the GUID as a key, retrieving the requested data. Since GUIDs are pretty much unguessable, this is much safer.

i would like to say sorry if i posted it here. Thats my thought. Anyways. Thanks for the information and idea given. If you are able to delete this post. You may delete the topic inorder to maintain the guidelines or topics that are much better in this section.